Automatic telephone system.



0. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 22, 1907.

Patented July 20, 1915.

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C. L. GOODRUM- AUTOMATIC TELEPHO Y'STEM.

APPLICATION FILED H] ,1907- 1,147,389. Patented. J 14 s s- C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 22, 1907. 1,147,389. Patented July 20, 1915.

l4 SHEETS-SHEET 3.

a mmtom co., WASHINGTON D c c. L. GO ODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPHCATION FILED JULY 221 i907.

Patented July 20, 1915.

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C. L. GOODRUM. AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 22. 1907.

1,147,389. Patented July 20, 1915.

14 SHEETS-SHEET 5.

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COLUMBIA FLANOORAPH 10-. WASHINGTON, D. c.

C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 22,1902.

1,147,389. Patented July 20,1915.

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C. L'GOODRUM; AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 22, 1907.

1,147,389. Patented July 20, 1915.

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APPLICATION FILED JULY 22. 1907.

Patented July 20, 1915.

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WW4 emu COLUMBIA PLANOGRAPH CO.,WASHINGTON, D. c.

C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

KPPLICATION FILED JULY 22.1907.

1, 147,389. Patented July 20, 1915.

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COLUMBIA PLANOGRAPH C(L, WASHINGTON. D4 6.

C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 22.1907.

14 SHEETS-SHEET l0.

Fig. 11.

COLUMBIA PLANOGRAPH C0.. WASHINGTON, D. c.

C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 22.1901.

1,147,389. Patented July 20, 1915.

14 SHEETSSHEET l 1.

c I {Z fij f l L Q/VUmeooeo COLUMBIA FLA-NOGRAPH CO.,WASHINC|TDN, D,

C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM. APPLICATION FILED JULY 22, 1901.

1,147,389. Patented July 20,1915.

l4 SHEETS-SHEET l2- val I QLT T- T IM -1|!! C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATTON FILED JULY 22. 1907.

Patented July 20, 1915.

14 $HEETSSHEET13.

C. L. GOODRUM.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JULY 22,1907.

Patented July 20, 1915.

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CI-IABLES LANE GOODRUIVI, OF ROCHESTER, NEIFI YORK, ASSIGNOR, BY MIESNE ASSIGN- MENTS, TO WESTERN ELECTRIC CQMPAIIY, OF NEW YORK, N. Y., A CORPORATION OF ILLINOIS.

Specification 0 Application filed July 22 To all 'LU/LOLL it may concern:

Be it known that I, CHARLns L. Goonnniz, of Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Automatic Telephone Systems; and I do hereby declare the following to be a full, clear, and exact description of the same, reference being had to the accompanying drawings, fonnng a part of the specification, and to the reference-numerals marked thereon.

The present invention relates to automatic telephone systems and it has for its object to pro 'ide a system of this character which shall so full metallic in every particular reip ring but two wires for each subscribers instrument circuit over which current for talking and signaling purposes is transmitted as well as the necessary currents which are despatched to control the operation of movable switcning mechanisms employed for connecting one subscribers instrument circuit to another. lhe switching mechanisms referred to comprise 'enerally finder and connector switches, the former operating automatically to pick up a calling line and'the latter acting in unison with impulses of current subsequently transmitted over said line to select a particular line with which it is desired to establish a connection.

Another object of the invention is to provide mechanism cooperating with said finder and connector switches by means of which signaling current-may be applied to the selected line to intermittently operate the calling devices or ringers at a called partys station. 7

The invention also comprehends the arrangement of apparatus to be used at the cen- "ral office or exchange for the distribution of traffic over a plurality of switching mechanisms or groups of such mechanisms. In this connection ertain switches are grouped in reference to one another and arranged for simultaneous operation, whereby two or more of them are started to pick up an instrument circuit on which a call has been originated, said switches cooperating with the circuit terminal in such a manner that the time required to select a given circuit is reduced to the minimum.

An additional attainment included'in the invention is the means by'which a busy test signal is automatically returned to a calling subscriber in the event an instrument circuit AUTOMATIC TELEPHONE SYSTEM.

f Letters Patent Patented July 28, 1915.

,1987. Serial No. 384,940. Y i i attained whereby the chief operator or clerk in charge thereof maybe fully informed at all times regarding the operativeness of each switch. In carrying out this feature of the invention a signal such as a lamp is employed which may, for instance, be located at the operators desk, the temporary lighting thereof indicating a callpassing through a particular switch or group of switches and its continued illumination being an indication of improper operation due to some line trouble which by this aid may be readily located.

i To these and other ends the invention consists in certain improvements and combinations ofparts all as will be hereinafter more fully described, the novel features being pointed out in the claims at the end of the specification.

In the drawings: Figures 1 and 2 are diagrammatic views illustrating generically the line connection as it is'effectedbetween two instrument circuits by means of the finder and connector switches, the operating mechanism of the switches being omitted, the first view showing thepositions of the switches in connecting instrument A with instrument B and the second illustrating the reverse connection. Fig. 3 is a diagrammatic view. of a plurality of telephone instrument circuits, showing the actuating and cut-off relays associated with each line. Fig. 4 is a diagraimnatic view (a continuation of Fi 3.) showing the arrangement of the terminals of said instrument circuits on a plurality of groups of finder and connector switches, with the traflic distributing mechanism controlling said groups of switches whereby two or more pairs of telephone instruments may be connected at the same time. In this figure the operating mecha nisms of the switches have also been omitted. Fig. 5 isa diagrammatic viewillustratinga llt) finder switch in conjunction with a plurality of instrument clrcults illustrating the controllingmechanism by means of which an instrument circuit on which a call is originated may be extended to the connector switch. Fig. 6 is a similar view of the conncctor switch showing the controlling mechanism by means of which said switch wipers are operated to select the terminals of the circuit of another telephone instrument to connect it to the extended instrumentcircuit shown in Fig. 5. Fig. 7 is a View similar to Fig. 5, illustrating in addition to the finder switch, a trafiic distributer switch mechanism and a signaling switch mechanism. Fi 8 is a complete assembled view of the mechanism employed in conjunction withthe connector switch showing the various mechanisms and the circuits controlling them by means of which the switch wipers are advanced progressively in one direction into an operative position and are released to restore them to their normal position, in conjunction with the devices employed for despatching signaling current over a selected instrument circuit, the devices for despatching the busy signal, which are operated in the event-that a selected instrument circuit is connected through some other-switch, or group of switches, and the apparatus which is actuated when the subscriber on the selected line answers in. Fig. 9 is a detail diagrammatic view of the motor magnet circuit of the connector switch. Fig. 10 is a similar view of the circuits established, when a particular line has been selected by the connector switch, to automatically despatch the signaling current over said line. Fig. 11 is a similar view illustrating the circuits over which the busy testis F 1g. 12 is a detail diagrammatic proper functions- Fig. lat is aplan view illustrating a type of switch which may be employed as finder, connector, distributing or signaling switches for operation with this system; Figs. 15 and 16 are detail sectional views thereof taken on the lines 15 l5 and 16 1G respectively. I

To facilitate tracingthe circuits refer-red o in the following specification, Figs. 3 and i should be placed together, the former above the latter; Figs. 5 and 6 should be joined, the former at the right hand side of the latter; and Figs. 7 and 8 should be similarly considered. The skeleton diagrams shown in Figs. 9, 10, and 11 inclusive, are reproductions of circuits also shown in Fig. 8.

Similar reference numerals in the several figures indicate similar parts.

In a telephone exchange system embodying this inventionthe connections between different telephone lines are automatically set up, or efiected, by apparatus arranged at the central oiiice or exchange, and the telephone lines or circuits leading thereto are divided into two classes comprising, first, incoming lines, or those on which calls are originated by subscribers who. desire to establish communication with other parties, and, secondly, outgoing lines over which the calls are despatched to signal said parties. Each line may, at different times, be of either class and it will, therefore, be understood whenthese lines are referred. to in the following description, that an incoming line or calling circuit is one leading from a subscribers telephone or station over which impulses of current are sent to connect said line, to an outgoing line and that the latteris the called circuit on which the signaling devices are actuated, when the connection has been set up or completed between the telephone instruments of the calling and the called subscribers;

In the system embodying the present in vention it is possible to connect by means of.

the central oilice, or exchange, apparatus a given line with any other line and to this end all the lines lead to terminals on a finder switch, or a plurality of such switches, and to similar terminals on an associate connect-or switch or switches. he finder switch performs the function of selecting an incoming line on which a call has been originated, and the connector switch, associated therewith, performs a similar function in selecting the outgoing line leading to par;-

ticular telephone instrument, or subscril a s station, with which the calling subscriber desires to communicate. The movable elements or wpcrs of the finder switch and its associate connector switch are tied to-' gcther, so that when the functions of each have been per-formed, the talking circuit, from the incoming to the outgoing line, is extended through them and may be retained until one of the two communicating.subscribers desires to effect a disconnection of said lines. i

in Figs. land 2 the above descibcd connccticns are shown diagrammatically, two separate instrui-ncnts being shown in each, and indicated generally by A and B, with a single finder switch F and a single connector switch C. In Fig. 1, the movable elements or wipers of the two switches are shown in instr y line Il -B lished from instrument A to instrument B when the circuit of the first mentioned instrument is the incoming line on which a call is originated, and in Fig. 2 these parts of the switches are shown in the position which they occupy when instrument B is the one on which a call was initiated.

The telephone instruments may be of the usual or any preferred construction compris ing generally a transmitter 1, a receiver 2, and the signaling devices or bells 3, all of which are arranged in the circuit of the line wires A.ri of instrument A, and B-l3 of instrument B. The instrument circuits are normally open at each suhscribers station at the contacts rL -B which are controlled by he receiver hook and are closed when the latter is released by the subscriber removing his receiver therefrom. Each pair of wires constituting the circuits of the telephone instruments is extended to the aforementioned switches located at the central office and terminate in immutable contacts located thereon, those of the wires AA being located on the switch F, as indicated by Ai -A the corresponding contacts on he switch 0 being indicated by A A said contacts being tied together by conductors A A the similar contacts of the wires 3-l3 on the switch F are indicated by E a) and on the switch C by'l3 B said pairs of contacts being also tied tocther by wires El -B The operating ncchanisms controlling the movable eleents or wipers of the two switches have con omitted from these illustrations but, as "ill appear more fully hereinafter, they are esigned to cause such switches to move progressively over a bank of contacts or terminals, representing a large number of tele phone lines. The wipers of the switch F are indicated by FF and those of the switch C by C-C the corresponding wipers of the two switches being connected by wires 4: and 5.

From an inspection of Fig. 1 it will be seen that the complete circuit between the in ".inients A and B may be traced as follows: instrument A, wire A", contact A, wiper F wire 5, wiper C contact 13, wire B, instrument B, wire B contact B wiper C, wire wiper F, contact A wire A instrumen' A. The foregoing is predicated upon the fact that the call originated at the ment A and the mechanism of the finder switch operated to pick up the contacts of the incoming circuit AA after which the switch C was actuated to connect said circuit with the terminals of the outgoing line l3l3 Supposing a reverse operation to be e ected in a like manner. The movable elements of the finder switch F tra its bank of contacts, or terminals, until reaching the terminals B B of the then the connector switch 0 cptails thereof being shown in Figs. 15 and 16. r

This switch is capable of performing the functions of either the finder, connector distributing or signaling switch, the only dif ference being in the number of brushes or wipers employed and the manner of wiring the contacts in their respective banks, as will be fully explained hereinafter in' connection with the diagrammatic illustrations.

The switch propercomprises generally a progressively movable member 6, which is adapted to be advanced step by step, and

to this end is made circular inform and is mounted upon a revoluble shaft 7 journaled:

at its lower end in the base plate 8, and sup ported at its upper end by a bearing on a bracket 9, the ends of which extend downwardly and are secured to the base plate, as shown in Fig. 16. Carried on the movable member and insulated therefrom are contact elements or spring wipers 10 and 11, corresponding to the wipers F-F ,-of'the switch F, and CC of the switch C. These elements are arranged one below the other and their outer ends are adapted to cooperate with a series of insulated terminal contacts 12 and 13, arranged in pairs corresponding to the contacts A ,A 'etc., those of each pair being located in vertical alinement, as shown in Fig. 15. As each switch controls a plurality of telephone lines, these pairs of terminals are supported upon a segmental bridge 14, and are arranged concentric with the center of move ment of the wipers. Beneath said contacts are other contacts 15 and 16 with which cooperate wipers 17 and 18, the purpose of all of which I will be subsequently described, but it may be here stated that the usual terminal contacts 12, 13, 15 and 16 are arranged in sets, each set being devoted to a single incoming instrument circuit, there being four contacts on the finder switch and three on the connector switch. The rear end of each wiper is provided with a s'egand the parts supported thereon to their normal position when they-are-released,-as shown inFig. 14.

The operating devices for advancing the movable elements or wipers comprise a pawl 21, pivoted to the upper end of an arm 22 on which it is moved by a spring 23 into engagement with teeth 24 on the periphery of the member 6. The arm 22 is pivoted at the point 25 and is provided with a laterally extending end 26, forming an armature, cooperating with the motor magnet 27, which armature is normally held in retracted position by the spring 28 bearing against the stud 29 on the arm 22, said spring also serving to advance the member 6 when the pawl 21 is in engagement therewith. A spring operated detent 30 serves to lock the movable element in adjusted position and at its outer end is a finger 31, projecting beneath the end of the pawl 21, the arrangement of the parts being such that when the pawl is moved downwardly into an inoperative positionthe detent will be retracted, as shown in Fig. 14. The means for effecting the release of-the member 6 comprises a spring latch member 33 having an end 34 which is adapted to hook over the edge of a lip 32 depending from the pawl 21. At its lower end the spring 33 is attached to an armature 35, pivotally supported in proximity to the release magnet 36, carrying an upwardlyextending arm 37 provided with a stud 38 with which cooperates a spring 39 normally tending to move the arm in a direction to retract the armature 35. Supported upon the base plate 8, in front of the spring 33, is a stud 40, which limits the lateral movement of the spring when the armature 35 is retracted, thereby permitting the lip 32 of the pawl to be disengaged from the hooked end of the spring, when said pawl is retracted by the energizing of the motor magnet 27 The movable member 6, controls two circuits, as will be further described in connection with the diagrammatic illustrations, which include a contact spring 41 playing between contact members 42 and 43, supported in a holder 44, on the base plate 8. The spring 41 has a normal tendency to engage the contact 42, but is held in engagement with the contact 43, when the member 6 and the contact elements carried thereon are in their normal position, by a pin 45 mounted on the member, which releases said spring upon the first step or movement imparted to said member;

The base on which the switch mechanism is mounted is composed of the part 8 supporting the bridge 14 and the part 8 carrying the operating devices and which may also be utilized as a support for relays operating in conjunction with the motor and release magnets. The parts of the switch base are detachable, the portion 8 being-adapted to berigidly connected to a suitable switch board frame and comprising side pieces between which the forward endof the part 8 is guided to insure the proper centering of the shaft 7 relatively to the are of the bank of contacts. This construction permits the operating mechanism to'be readily removed for inspection or adjustment of its-parts which is an advantageous feature in apparatus of this charac ter because it is customary to arrange a lar e number of these switches compactly in rows and tiers to economize space, so that unless the working parts are removable considerable diiiiculty is experienced when'it becomes necessary to correct some fault in their operation.

The finder and connector switches are actuated by electromagnetic devices peculiar to each, those of the finder, switch being antomatically set into operation, and controlled by secondary circuits, which are established when an instrument circuit is closed at the subscribers station, and the mechanism of the connector switch is rendered operative when the finder switch has picked up the incoming or calling circuit and is controlled by impulses of current which may be despatched by a suitable form of impulse transmitter located at the subscribers station, to select a given outgoing line, or called circuit. Accordingly the instrument circuit, comprising wires AA is extended, as indicated at A A Figs. 1, 2, 3, 5 and 7, to normally closed contacts A one of which is mounted upon a spring finger provided with a projection 46 adapted to cooperate with teeth on an impulse transmitter A to thereby transmit or send over the operating circuit one or more impulses of current, when the circuit is closed at the hook contacts A.

The electromagnetic mechanisms for causing the various switches to perform their re spective functions, are all adapted to be operated from a common battery, but in order to facilitate the description and illustration, and render a more comprehensive understanding of the various circuits to be had, these are shown in the various diagrammatic views as receiving current from different sources or sets of batteries Z Z etc. To render the circuits easy to trace they are shown with the conventional ground or earth connections, but it will be understood that where the term ground is employed and shown, it refers to a connection leading directly to one side of the main battery, so

that a telephone system embodying this invention, when installed in working order, is entirelyfree of the so-called grounds employed for actuating parts of the apparatus, thereby eliminating line disturbances or other troubles attributable to this cause;

Trafiic cZ8zfributz'0n.The simplest phase of the system has been explained in connec.

tion with Figs. 1 and 2, but as such an arrangement of parts only permits intercommunication between two subscribers at the same time, it is desirabl to provide a plurality of groups of associated finder and connector switches, on each of which appear the terminals of all instrument circuits, and to combine with said groups a distributing mechanism by means of which two or more subscribers may connect their telephone instruments in pairs and carry on private conversation with each other. This grouping of the switches is illustrated in Fig. 4:, which shows three sets of finder and connector switches, said groups being indicated by I, II and III. The corresponding terminals of each instrument circuit appear in the banks of contacts of all of the finder and connector switches and are connected by the trunk lines in the manner illustrated in Fig. 4. These trunk lines are ramifications or branches of the instrument circuits, such as those shown in Fig. 8, and although only three groups of switches have been shown, it will be understood that the number of these may be increased in reference to the total number of lines servedfand the percentage thereof which it may be desired to accommodate at one time. It has been determined from actual practice that the number of calls received at any one time does not, as a rule, exceed ten per cent. of the total number of telephone instruments. Any desired number of. groups of finder and connector switches, may be installed so that a given ratio of calls may be accommodated at the same time, successive calls being put through different groups of switches by the tralfic distributing mechanism, as will appear more fully hereinafter.

To illustrate the above described grouping of switches and the distribution of calls thereover in a graphical manner, six telephone instrument circuits have been shown in Fig. 3, which are indicated respectively by A, B, G, H, I, J. Instruments A and B in Figs. 3 and 4-, are shown with the same circuits illustrated in Figs. 1 and 2, and the circuits of the other instruments are identical therewith and are indicated by appropriate reference characters, both capitals and small letters, provided with proper exponents, so that detailed description of these may be omitted. From an inspection of Fig. 4L it will be seen that the contact banks of each finder and connector of each group contain terminals for all of the instrument circuits which are joined by the trunk connections, such as A A B B In group I, of this figure, the instrument A is con nected to instrument B, in the same manner as shown in Fig. 1. Group II shows instrument H connected to instrument G, the terminals H and H being engaged bythe brushes of the finder switch and the termi nals G, G of the circuit of instrument G, being engaged by thebrushes ot-the associate connector switch. In group III the brushes of the two switches are each shown in their normal position in readiness to connect a third pair of instrument circuits, persition to actuate, in a like manner, the op crating devices of the finder switch of the. second group II, allowing the wipers oi this switch to traverse their bank of contacts to engage the terminals of-the line sending in the second call. ation the trafiic distributer advanced in F ollowing this last operreadiness to subsequently actuate the rc- I maining group of switches III, upon receiving a call originated on any line. The

third call mightbe despatched from either instruments I or J, or if the switches or" group I should be released and either sub scriber A or B attempted to establish another connection, it would be eifected over the switches of group III. I

The tratfic distributing mechanism" indi-. cated by D, is illustrated generally in Fig. 4%, but as its operation is dependent upon the operation of the finder and connector switches, it will be referred to more particularly hereinafter.

The finder switch.-To enable a comprehensive understanding to be had of the various features of the invention, itwillbe advantageous and facilitate an understanding of the system to first take up the'various steps performed in connecting two instrument circuits over a single group of switches, it being understood at the outset that this operation is precisely the same on each group, the only difference being that said groups are operated successively by the movements occurring in the trafiic distributing mechanism. One. group of switches corresponding to the group I, shown in Fig. L, is illustrated in the combined views Figs. 5 and 6, the former illustrating the finder switch mechanism and the latter that part of the connector switch by means or" which it may be actuated by impulses of current despatched from a subscribers instrument to select the terminals of another circuit.

In Fig. 5 the circuits of telephones A, B and J have been reproduced, with each of which is associated actuating. relays A B and J respectively, which are arranged at the central oflice and are adapted to be energized when their respective instrument circuits are closed to start the operation of the distributer D and the linderswitch l but to simplify the description at this point the is shown with a plurality of sets or they tour terminal contacts arranged in rows, as

shown in Fig. 15,, those constituting the lower pair of the set related to the circuit of instrument A being indicated by f and 7. Leading from the contact is a wire A connected to one end of the c'ut-ofi relay A, the other terminal thereof being supplied at certain times with current from the battery Z; another wire A leads from the contact 7 to a back contact a with which the armature a of the actuating rel'ay non mally engages,- said armature haying a groimded connection 2 One end or the coil oil? the actuating relay A isconne'ctcd to the battery Z? and its other extremity is connected to a back contact a with which normally engages the armature a i the cut of? relay, said armature being connected to one side of the instrument circuit by a wire a joined to the wire A Asecond armature controlled by the cut -oil relay, indicated by a, is connected by a wirea, to the other side A of the instrument circuit. This armature normally engages a back contact a also grounded at 2 V 7 It has been explained in connection with Figs. ll, 15 and 16 how the movable contact elements coeperate with the several terminals of the bank of contacts of each set, but in Figs. 5 and 6 the illustrations are simplified by showing the circuit wires connected directly to the wipers, while in reality they are connected to brushes such as 10", etc. shown in Fig. 16. Referring now par- .ticularly to Fig. 5, it will be seen that the brushes F, F are extended by the wires t and 5 through normally closed contacts on armatures of a relay F which will be described more fully hereinafter, the function ascribed thereto being that oi": opening the extended instrument circuit during'the rotation of the brushes of the finder switch in one direction, to pick up an incoming line, and when they are returning in the opposite direction, to their normal position. The opening of the ties between the switches eliminates any vibration in the receiver of a subscribers telephone, as said brushes rotate over the coerdinate contacts of other instru- 'men't circuits which may have been previ ously connected over another; group of switches, and it also prevents any possible interference with the mechanism of the as sociatc connector switch during the operation of its finder switch.

. Operating conjointly withthe motor magnet 27 is a relay P, which performs the function of temporarily closing the holding circuit of the motor magnet; actuating the relay F opening a circuit ofone of the switch wipers, to prevent the actuation of the cut-oil relays until the calling line has been found; and, also, to open the circuit of a switching relay, which has not been before mentioned, and is associated with the connector switch. The operating circuit of the motor magnet is a secondary circuit over which current is supplied to cause its con tinuous operation until the wipers of the switch F have picked up the incoming line. The finder switch mechanism is adapted to be operated whenever one of the instrument circuits is closed and to continue its move-V which the armature a engages when the actuatingrelayA is "energized. The other "extremity of the booster line, indicated by 7 terminates in the spring controlled switch arm 7 which is normally held in engagement with the back contact 7 by the pin f said contact being connected by the wire f to a terminal F, with which cooporates the armature f actuated by and arranged in the circuit of the motor magnet 27 to one end of the coil of whichit is connectec by the wire 7, the other extremity of said coilbeing supplied with current from the battery Z starting circuit also includes the relay F to which it is extended by the wire 7, said The booster line or relay receiving current from the battery Z over the wire F. The secondary operating circuit for the motor magnet leads over the wire f to a back contact f, with which cooperates an armature f, on the relay F connected by the wire 7 to the switch wiper f The relay F (similar to relay F is associated with the release magnet 36* and is adapted to operate in conpinctio'n therewith and with the release magnet of the associ* ated connector switch C whereby both switches may be simultaneously released and 

